Santu Sarkar

Bio: Santu Sarkar is an academic researcher from University of Calcutta. The author has contributed to research in topics: Bit error rate & Optical fiber. The author has an hindex of 2, co-authored 15 publications receiving 14 citations.

A study of nZVI DTPA induced degradation of selective organic pollutants by the help of ac conductivity measurement

Abstract: In this work, diethylene triamine pentacetic acid (DTPA) stabilized nano scale zero valent iron (nZVI)) has been synthesized through co precipitation method. A systematic characterization of DTPA stabilized nZVI has been performed. It has been found that DTPA stabilized nZVI is well dispersed with less aggregation. Average particle size obtained is within 50 nm. In the presence of ultrasound irradiation (US), the degradation of some water pollutants like methyl orange (MO), azo based textile dyes and phenols by the help of DTPA stabilized nZVI is recorded over 95 %, 85 %within 10−15 min and 70 % within 30−40 min respectively. In this work, the ac conductivity of different water pollutants during degradation has also been studied which shows prominent distinguishable characteristics and helps to get an idea about the degradation of the pollutants without using spectrophotometric analysis. Reusability of nanoparticles was monitored in this work up to three cycles. 85 % MO degradation have been observed up to the last cycle.

A new approach to teach molecular biology in high school using Python

Abstract: Teachers' role in 21st century is undergoing a transition from the orthodox ‘chalk and talk’ method to a student-centered, activity-based approach that maximizes students' active-learning opportunities and engages them to solve various problems. Teachers play an important role in today's technology-rich classrooms that significantly affect students' learning. For this reason it is time for the students, taking up biology in senior school, to realize that their responsibilities towards the subject have changed, since recent trends in information and communication are redefining biology and taking precedence over the traditional methods. The present study is designed to investigate the utility of Python programming language as a teaching material for high school students in learning biology. This paper also highlights the strengths in using Python Language in some selected topics of biology and establishes how there is a connection between student successes in learning biology with creative use of Python programs.

A probabilistic framework to estimate minimum Bit Error Rate in a WDM receiver with component crosstalk

Abstract: The objective of this work is to analyze the performance degradation in a Wavelength Division Multiplexing (WDM) receiver system in presence of multiple component crosstalk sources and to estimate the value of optimum detection threshold which will ensure minimum Bit Error Rate (BER). For this a probabilistic approach is introduced which considers all probable combinations in the interfering channels and their realistic impact while calculating BER. BER considering the presence of signal-crosstalk beat noise is formulated and the effect of the variation of number of interfering channels, crosstalk level, receiver thermal noise and photocurrent have been investigated and compared to the experimental findings and existing worst case analysis model. Some optimum detection threshold values providing minimum BER are also suggested and compared with the previous results which are essential for improvement of the practical receiver design.

Investigating Ionospheric Scintillation Effects on Multifrequency GPS Signals

Abstract: Over the last 15 years, the satellite constellation of the global positioning system (GPS) has been modernized for more precise applications, with the introduction of the L2C and L5 signals. However, among other effects, they are susceptible to severe ionospheric effects, particularly in the equatorial and low-latitude regions. Equatorial plasma bubbles, resulting from the combination of the ionospheric electrodynamics with plasma instability mechanisms and thermospheric coupling, may generate irregularity structures with scale sizes ranging from hundreds of kilometers to a few meters (or less). Ionospheric irregularities may cause deep amplitude fades and phase shifts to transionospheric signals. That is, they are responsible for amplitude and phase scintillation, which degrade receiver operations and may cause failures and unavailability to positioning and navigation services under extreme conditions. The objective of the present work is to analyze ionospheric scintillation effects on the L2C and L5 GPS signals, to compare their vulnerabilities with those of the L1 signal. The data used in this analysis were collected between November 2014 and March 2015, during the maximum solar activity of cycle 24 (a period of great scintillation incidence), by scintillation monitors deployed at four different sites in the Brazilian territory: Fortaleza, Presidente Prudente, Sao Jose dos Campos, and Porto Alegre. Intensity fades will be analyzed, considering different thresholds, to reveal their empirical probability distributions of scintillation occurrence, average fading occurrences and durations. The results will show that greater probabilities of strong scintillation occurrences are present in the modernized signals, reaching up to five times more events in the L5 signal in comparison with those in the legacy L1 signal. It will be shown that the L5 average fade duration is distinctly longer than the corresponding ones for the other frequencies, considering the same site, threshold, and L1 amplitude scintillation level. The results will also show that the average fade duration decreases according to the average ratio 0.6 s/3 dB within the threshold range from − 6 to − 15 dB, considering the same amplitude scintillation level and location.

AOX degradation of the pulp and paper industry bleaching wastewater using nZVI in two different agitation processes

Abstract: The pulp and paper industry has been researching different treatments for the degradation of adsorbable organohalogens (AOX). In this work, two agitation processes (mechanical and ultrasound) were analyzed in the AOX degradation of the bleaching wastewater using nano zero valent iron (nZVI). The work used different variables for the AOX removal process, such as pH, time, nZVI, and hydrogen peroxide (H 2 O2) concentration. Results show an increase in AOX degradation when a higher nZVI concentration is used. The optimal combination of variables for the treatment with mechanical agitation was found in the ratio 2:5 (nZVI : H 2 O2), degrading 85% of AOX in 60 min, with acid pH. Ultrasound treatment consisted of half process time and less degradation than mechanical agitation treatment. The 2:5 ratio in ultrasound agitation degraded 55% of AOX within 30 min at the end of the process. Both methods of the homogenization process of zero valent iron nanoparticles in the bleaching wastewater of the paper and cellulose industry are efficient. However, the mechanical stirring process has a more significant potential for AOX degradation. The variables (pH, concentration of nZVI and H 2 O2 and duration of the process) used in the bleaching wastewater treatment process must be considered for future implementation in the pulp and paper industry.

Bibliometric analysis of zerovalent iron particles research for environmental remediation from 2000 to 2019

Abstract: Zerovalent iron (ZVI) has been a major focus of research and has attracted great attention during the last 2 decades by international researchers because of its excellent pollutant removal performance and several other merits in environmental remediation. Based on Web of Science Core Collection data, we present a comprehensive bibliometric analysis of ZVI research from 2000 to 2019. We analyze 4472 publications assuming three stages of growth trend of annual publication totals. We find that “The Chemical Engineering Journal” has been the most productive journal; Noubactep C is identified as the most productive author; China has been the most active country in this field and the Chinese Academy of Science the most productive institution. The timeline of keywords shows seven distinct co-citation clusters. In addition, the top 38 keywords with strong citation bursts are also detected, suggesting that the innovation of green composite synthesis of ZVI and nanoscale ZVI and its efficient removal capacity might be the prevailing research directions in the future.

Examining the Tolerance of GNSS Receiver Phase Tracking Loop Under the Effects of Severe Ionospheric Scintillation Conditions Based on Its Bandwidth

Abstract: This study aims to evaluate the performance of phase-locked loop (PLL) under the presence of distinct scintillation patterns in the signal. Scintillation is very common in low-latitude regions due to the ionospheric dynamics. Under strong scintillation scenario the occurrence of deep fading events is usually registered and may cause severe degradation in the communication. The investigation conducted in this study uses the amplitude scintillation index S 4 , the decorrelation time τ 0 , and the bandwidth B n as main parameters. The study evaluates 54 different combinations of these parameters. The results indicate that in order to minimize the occurrence of cycle slips in the output phase of the PLL, the most appropriate tracking loop bandwidth B n depends on the values of both S 4 and τ 0 , which characterize the scintillation fading pattern. Simulations showed that as the S 4 index increases, the automatic increment in the PLL bandwidth may not be the best choice as the performance depends on the temporal characteristics of the scintillating signal. The analysis showed that, among the configurations tested, the equivalent noise bandwidth of 10 Hz achieved the best performance overall. The investigation also showed that choosing the wrong parameter regarding the PLL bandwidth may increase the probability of cycle slip by up to 10 times during fading events.